Field of the Invention
The present invention relates to a substrate peripheral portion measuring device for measuring the state of the peripheral portion of a substrate. The substrate peripheral portion measuring device belongs to a semiconductor wafer peripheral portion polishing apparatus, for example, and is used to measure the polishing state of the peripheral portion being polished.
Background
As miniaturization and high integration of a semiconductor device advance, management of particles becomes more important. One of major problems in the management of the particles is the dust formation, which is caused by the surface roughness to occur on the circumferential peripheral portion of a semiconductor wafer (or substrate) while the semiconductor device is being manufactured.
In the semiconductor device manufacturing process, flaws or a number of minute needle-shaped projections may be formed at the circumferential peripheral portion of the semiconductor wafer thereby to cause the surface roughness. The needle-shaped projections are broken to produce the particles while the semiconductor wafer is being transferred or processed. These particles lead to a drop in the production yield. Thus, it is necessary to remove the needle-shaped projections from the circumferential peripheral portion of the semiconductor wafer.
In recent years, moreover, there is a tendency that Cu is used as the wiring material for the semiconductor device and that the Low-k material is used as an insulating material. When the Cu formed on the circumferential peripheral portion of the semiconductor wafer sticks to the arm of a transfer robot or a cassette for housing the substrate, the Cu can cause the so-called “cross contamination”, in which it diffuses to contaminate the remaining steps. On the other hand, the very fragile Low-k film leaves the circumferential peripheral portion of the substrate during the CMP working treatment thereby to damage or scratch the pattern face. It is, therefore, important to clear the circumferential peripheral portion of the semiconductor wafer of the Cu or Low-k film.
As the pattern of the semiconductor wafer becomes highly dense, the sub-micron contamination is deemed as a problem and highlighted as a serious cause for a defect in the wafer process, although not deemed serious in the prior art. Under this background, it is also important to polish off the film or the like of the wafer peripheral portion.
In the general peripheral portion polishing technique of the prior art, the turning wafer is fed with a liquid such as water. A polishing tool such as a polishing tape is pushed to the peripheral portion thereby to polish the peripheral portion.
The prior art cannot grasp the state of the peripheral portion being polished. Therefore, a total polishing time is determined to manage the polishing process. In order to determine the total polishing time, the sample wafer is subjected at first to a polishing treatment of an initial stage, and the wafer end face is then observed by a camera thereby to examine the flaws left in the defective portion. Then, an additional polishing time necessary for a target finish state is calculated, and the additional polish is performed. The additional polishing time is calculated by using a polishing rate. The additional polish and the subsequent camera observation are repeated to determine the total polishing time. The total polishing time thus obtained is applied to the subsequent wafer polish.
Moreover, a wafer peripheral portion measuring device has also been proposed in the prior art. For example, the measurement device of JP-A-2003-139523 (pages 3 and 4, FIG. 1) illuminates the peripheral portion with a diffusive light to photograph the peripheral portion thereby to detect the defect of the peripheral portion from the photograph.
In case, however, the total polishing time is determined by means of a sample wafer, it takes a remarkably long time to repeat the additional polish and the camera observation. Moreover, the total polishing time required for the practice is different for each wafer. Even if the total polishing time is determined with the sample wafer, the polish may be short or excessive for another wafer so that the process is not stabilized to lower the productivity.
On the other hand, the wafer peripheral portion measuring device of the prior art has failed to consider the measurement in the presence of a liquid such as water. Therefore, the device of the prior art is not suited for the measurement in the peripheral portion polishing apparatus (i.e., in-line) and during the polish (i.e., in situ). If the peripheral portion could be measured during the polish in the polishing apparatus, the peripheral portion polishing process could be properly managed to improve the productivity.
Here, the background art of the invention has been described on the polish of the wafer peripheral portion. A similar background can apply to purposes other than the peripheral portion polish. For example, there is desired a technique for measuring the peripheral portion in the rinsing process.